Catalytic treatment of carbonaceous materials



I Patented Jan. 8,1946

CATALYTIC TREATMENT OF CABBONACEOUS MATERIALS Bernard S. Greensfelderand William A. Bailey,

Jr., Oakland, Calii'., assignors to Shell Development Company, SanFrancisco, Calif., a corporation of Delaware No Drawing. Application May9, 1944, Serial No. 584,808

' This invention relates to the treatment of carbonaceous materials atelevated temperatures under substantial hydrogen pressure in thepresence of catalysts to prqduce lower boiling products having anenhanced ratio of hydrogen to carbon. Treatments of this kind have beenreferred to in the past as destructive hydrogenations. This designationmay have been approprlate for previous methods of operation in which thereaction was to a very large extent an u'ncontrolled decomposition ofthe starting material with a more or less concurrent addition ofhydrogen to the resulting mixture of products. It

does not adequately characterize the present of the periodic table havebeen stressed because they retain their hydrogenation activity in thepresence of impurities, such as sulfur compounds, usually present in thefeed stocks. The products obtained in the past, however, have-not beenof the most advantageous quality, particularly in respect to the engineperformance characteristics of the motor fuels produced. I

It is an object of the present invention to eliminate, or at leastreduce, the foregoing and other disadvantages of previous methods oftreating carbonaceous materials with hydrogen to produce lower boilinghydrocarbons of higher hydrogen content. Another object is to providemore advantageous catalysts for reactions of this type.- A furtherobject is to produce gasolines of improved octane number and engineperformance characteristics from higher boiling carbonaceous materials.Still other objects and advantages of the invention will be apparentfrom the following description of a preferred method of carrying out theinvention. v

The conversion of solid carbonaceous materials such as coal, etc., intomarketable liquid hydrocarbons by hydrogenation is usually performed ina plurality of stages. First, the coal is made into a paste with heavyoil, the catalyst is added and the mixture treated with hydrogen atpressures of 200 to 1000 atmospheres and about 4&0 to 500 0., forexample. The wide boiling range oil thus produced contains a substantialamount (50% to 55%) of heavy oil which is separated and used to preparecoal paste for further treatment. The middle boiling range 011 (lowerboiling products of about 300 to 400 C. end point) is subjected to asecond destructive hydrogenation stage to increase the yield ofgasoline. For clarity, the invention will be described with particularreference to the treatment of intermediate boiling range hydrocarbonswhich comprise the feed to the second stage of destructivehydrogenation. This description will serve to illustrate the principlesof the invention since the same methods of operation may be used for thetreatment of petroleum products, coal tars, shale oils and the like.However, the invention is not limited thereby with respectto the sourceor nature of the feed stocks, or as to the particular manner oftreatment of any carbonaceous material capable of destructivehydrogenation. According to the invention, hydrocarbons of improvedproperties are produced by treating higher boiling carbonaceousmaterials with hydrogen at pressures above about 200 atmospheres in thepresence of a new catalyst comprising essentially alumina and boricoxide. Mixtures of alumina with silica and other diflicultly reducihieoxides have been proposed as carriers for a wide variety ofhydrogenation catalysts and it has also been suggested in some casesthat small amounts of boric acid may ormay not be incorconstituent whichco-actswitfi'the boria to infiuence the reactions of the invention in anadvantageous manner which is not achieved by the use of eitherconstituent alone or by either constituent in other combinations. Thus,neither the alumina alone nor the mixture of alumina. and boria is to beregarded as merely a support for a hydrogenation catalyst, even if suchshould be present. Rather, the. specific mixtures of alumina and boriaused constitute the active catalysts in the process. It was not to beexpected that catalysts of this type would be advantageous for thesereactions because they are not hydro- "genation catalysts in theacceptedsense of the term. since, for example, they are not capable of effectingsubstantial addition of hydrogen to lower olefins under the usualhydrogenation conditions for'suchyreactions. Nevertheless, in theprocess of the invention these catalysts not only serve to. promote-adesirable mode of hydrogenation but also have an. advantageousisomerizing 1. action. y ldi p oducts of excellent engine performancecharacteristics, accompanied by, only a low amoimt of degradation togaseous hydrocarbons. v

The desired properties of the new catalysts can be obtained only by theuse of alumina in, the proper form. Either crystalline or gel'aluminasmay be employed. Thus the alumina maybe a porous alpha or beta aluminatrihydrate.

going'types of alumina or a synthetic alumina gel maybe used. In anycase, for production of a highly active catalyst it is essential thatthe alumina have a specific surface of at least 100 square meters pergram as determined by the method of Emmett and Brunauer and a bulkdensity of between about 0.4 and 1.0 gm./cc. at the time of preparationof the catalyst. These prop erties are fixed by the methods used forpreparation and treatment of the alumina. The spexerogel or crystallineA1203 WitinHaBQni E perature preferably greater than 75C. Shah beemployed to yield a high B20: content. The

boron compounds which may be decomposed to mixture is then calcined, atabout 200 to 600 C.

to convert the boric acid to boric oxide. Other the. oxide by heating inthis range or at lower temperatures may be used-instead of boric acid.

For both gel and crystalline aluminas the boric oxide may be applied insolution in an alcoholic solvent. Alternatively, the alumina may be im-'f alpha alumina monohydrate or gamma alumina. Furthermore, the aluminamay be in the form of a porous natural or calcined bauxite consistingpredominantly of one or more of the forecific surface of the finalcatalyst is also preferably v at least 100 square meters per gram butmay become lower during use while still remaining usable although lessactive.

Siutablecrystalline aluminas may be obtained, for example, by the slowcrystallization of .alpha alumina. trihydrate or beta alumina trihydratepregnated by exposure. to water vapor carrying hydrated boric oxide, orto vapors of an alkyl borate which will leave a residue of B20: whendecomposed by heating. It is sometimes advantageous when using gel formsof alumina to incorporate the chosen compound in the alumina during theprecipitation step. In such cases it is of course not feasible to washtheprecipitated gel or to subject it to any other subsequent treat-"ment which would remove the added boron compound. Consequently, morecareful control of'th precipitation is necessary in order to avoidinclusion of undesirable constituents in the finished catalyst.

It is essential that the catalyst contain between 6% and 30% B20: basedupon the total weight of A120: and B20: present and most preferablybetween about 8% and 25% is used. Lower concentrations ofboric'oxidegive inferioreatalysts and excessive amounts are alsodetrimental. In some cases two or more impregnations and calcinationsmay be necessary in order to incorporate the desired amountof boria.

Regardless of the method of catalyst prepare tion used it is importantthat a suitable heat treatment to activate the catalyst and insure thedesired surface characteristics be provided. As

from alkali .aluminate solutions followed by par- Suitable alumina gelsmay be prepared by sevv eral different methods. One convenient way is toprecipitate an alumina gel from a solution of a soluble aluminum saltsuch as the nitrate, sulfate or chloride with abuse such as ammoniumhydroxide or sodium hydroxide. Instead of aluminum salts, ametalaluminate or aluminum amalgam may be used in preparing the alumina gel.

-Whatever the method of precipitation used, it

may be desirable to remove the precipitant from oxide. Excessive amountsof alkali metal salts reduce the activity of the catalyst and may beremoved by water washing the gel. The properties of the final catalystmay be improved by pepthe alumina prior to incorporation of the-Doric vpreviously indicated, this treatment may advantageously be applied tothe alumina prior to incorporation of the boron. However, it is alsofeasible to activate the catalyst by heating after incorporation of theboric oxide by any of the previously described methods. Heating at atemperature above about 250 C., for example between about 300 and 600C., until the alumina is substantially converted to the alphamonohydrate or gamma form is a suitable method of activation. Smallamounts of silicon or titanium dioxide may also be incorporated in thecatalyst to increase its surface further, but such oxides shouldconstitute-not more than 20% by weight of the finishedcatalyst.

The amounts of other constituents should also be carefully controlled inorder to lnsurethe desired activity and selectivity of the catalyst.

Thus, for example, the iron content should be below 3% and preferably isless than 1%.

The conditions used in carrying out the process of the invention withthe new catalyst vdepend upon the particular material being treated andthe type of product desired, and may vary considerably. In all cases,however, it is essentization of A120: in. the hyrogel, xerogel, orcrysexample.

' talline state by treatment with acetic acid, for

The boric oxide maybe incorporated into the alumina in'a number ofdiflerent ways. when alumina in gel form is used, the desired amount ofboria may be incorporated'by homogenizing the wet hydrous gel with boricacid or by imp egnating the hydrous or dried gel with a boric tial thatthe pressure he maintained above 200 atmospheres. A hydrogen feed ratioabove one mole per mole of hydrocarbon treated is also desirable.Temperatures between about 250 and about 600 C. are genera-lly suitableand the hydrocarbon feed rate may vary from about 0.1 to about 10volumes per volume of catalyst per hour. These conditions areinterdependent and the optimum for any one factor, while ordinarilyfall- 7 ing within the foregoing limits, will depend upon the otherconditions used.

acid solution. In the .case of impregnation of The process of theinvention may be carried g alysts of th invention.

lyst case; the hydrocarbon to be treated may be in liquid, in mixedliquid-vapor, or in the vapor phase, and is passed together withhydrogen over the catalyst under the appropriate reaction conditions.For such operations it may be desirable to have the catalyst depositedon a support of suitable inactive material, such as kieselguhr amongmany others. Such supports are not at all essential; thus, whenoperations are carried outwith the catalyst in finely divided form andsuspended in the fluid hydrocarbon to be treated, catalyst supports arepreferably not used.

As previously pointed out, the process and catalysts of the inventionshould give gasoline boiling products which equal or excel (particularlyin regard to engine performance characteristics) those obtained by otherprocedures' Thus, for example, one of th best-known prior art methods of"destructive hydrogenation uses as catalyst tungsten sulfide depositedon a montmorillonite type support such as hydrogen fluoride treatedTerrana or Super-Filtrol." When this catalyst is used for thedestructive hydrogenation of Elwerath gas oil employing the followingreaction conditions:

Temperature C 400-420 Pressure atmospheres 250 Total hydrocarbon feedrate kg./l./hr 1 Hydrogen rate m. /hr./l 2

Alumina (substantially gamma form) "per cent-.. 75

Boris clo.. Y Ines on ignition do 9 Surface area "so. meters/gram 300Bulk density 0.85 Iron per cent max 0.2

Using a catalyst of this type a similar yield of gasoline hydrocarbonsboiling below 180? C. and having an octane number of 75/76 should beobtained while operating under the above-named conditions except for thenecessary elevation of the pressure to 600 atmospheres.

The catalysts of the invention have along effective lite in the process.Stability to high temperature is a salient characteristic of the cat-Theymay be readily regenerated in case of loss of activity resultingfrom the deposition of carbonaceous material on their surface.Regeneration with air or oxygencontaining gases is readily secured withthese catalysts, whereas those incorporating a heavy metal sulfide maybe permanently injured and at best must be subjected to carefulre-sulflding treatment after exposure to air or oxygencontaining gases.A'ny tendency for the catalyst to lose boria during regeneration or innormal steam containing boric acid into the reactor. The added boricacid may be converted to boric oxide operations may be compensated forby adding v boric acid to the catalyst in place, by passing eitherbefore or during subsequent use of the catalyst for conversion of thecarbonaceous material being treated. Still other variations in theprocess may be made. and it will be understood that the invention is notlimited to the details disclosed by way of illustration nor by anytheory advanced in explanation of the more advantageous resultsobtained.

We c as our invention:

1., A process of producing lower boiling hydrocarbons in the gasolinerange which comprises treating a higher boiling carbonaceous materialwith hydrogen under a pressure 0! at least 200 atmospheres, at betweenabout 200 and 600 C. in the presence of a catalyst containing less than20% silica comprising alumina and boric oxidein which the boric oxidecontent is between and 30% of the total weight of alumina and boricoxide, said catalyst having a specific surtace of at least square meters.per gram,. a bulk density between about 0.4 and 1.0 and containing lessthan 3% iron and not more than 2% sodium.

2. A process or producing lowerboiiing hydrocarbons in the gasolinerange which comprises treating a higher boiling carbonaceous materialwith hydrogen under a pressure of at least 200 atmospheres, at betweenabout 200 and 600 C. in the presence oi as catalyst containing less than20%5 silica. comprising a porous gamma alumina having a specific surfaceof at least 100 square meters per gram, having thereon between 6.4% and43% of boricoxide, said catalyst having a bulk density between about 0.4and 1.0 and containing less than 3% iron andnot more than 2% sodium.

3. A process of producing lower boiling hydrocarbons in the gasolinerange which comprises treating a higher boiling carbonaceous materialwith at least an equal molecular amount of hydrogen under a pressure ofat least 200 atmos-.

pheres at a temperature between 200 and 600 C. in the presence of analumina gel having a specific surface of at least 100 square meters pergram admixed with between 6.4% and d3% or boric oxide based on theweight otalumina present, said catalyst containing less than 20% silicaand having a bulk density between about (PA and 1.0 and containing lessthan 3% iron'and not more than 2% sodium.

' 4. A process of producing lower boiling hydrocarbons from higherboiling carbonaceous material which comprises contacting said higherboiling material and a substantial molecular excess of hydrogen under apressure of at least 200 atmospheres at between 200 and 600 C. with acatalyst containing less than 20% silica prepared by impregnatingaporous alumina with boric acid and" subjecting the resulting mixture toa heat treatment to convert said acid to boric oxide and form asilica-free catalyst containing 6% to 30% boric oxide based on the totalweight of boric oxide and alumina present and having a 20% 7momprlsWnTniTnTboHeoxide in ch the boric oxide content is between 8% and30% of the total weight of alumina and catalyst consisting of aluminaandboric oxide containing between 6% and 30% oi boric oxide by weight.

6. A process of producing lower boiling hydrocarbons Irom higher boilingcarbonaceous ma-.

'terial'which comprises contacting said higher boiling material and asubstantial molecular excess of hydrogen under a, pressure of at least200 atmospheres at between 200 C. and 600 C. in

the presence of a catalyst containing less than "i boric oxide, saidcatalyst having a, specific surface of at least 109 square meters pergram, a bulk density between about 0.4 and 1.0 and containingless than3% .iron and not more than 2% sodium. t

BERNARD S. GREEN WILLIAM A. BAILEY, J2.

